An illumination device generally employs at least one light source to emit light, such that the illumination device may be applied into various conditions. Since a light-emitting diode (LED) has many advantages, such as long lifetime, low power consumption, high luminance, and good environmental protection, etc., it has been widely used in the illumination device as the light source.
Referring to FIG. 1, a typical illumination device 10 is provided. As shown in FIG. 1, the typical illumination device 10 may be a projection lamp, which may comprise a light source 11, a lens 12, an integration rod 13 and a reflector 14. The light source 11 includes various LEDs, such as red LEDs, green LEDs or blue LEDs. Lights emitted from the red LEDs, the green LEDs and the blue LEDs pass through the lens 12 and are mixed in the integration rod 13. Then, the light reflected by the reflector 14 so as to be collected to the axis of the integration rod 13.
However, the typical illumination device 10 used as the projection lamp is prone to generate ghost images and stray light. Furthermore, the typical illumination device 10 used as the projection lamp does not have a zoom function, and cannot project specific light patterns, and has a low contrast ratio.